Inductor alternator

ABSTRACT

A transducer includes a stator formed of a magnetisable material and arranged to define at least one pair of adjacent pole pieces, and a rotor formed of a magnetisable material and arranged to define at least one pole piece. The rotor is movable angularly with respect to the stator from a first position, in which the one rotor pole piece is aligned with but spaced from one of the pair of stator pole pieces by a predetermined air gap, to a second position, in which the one rotor pole piece is aligned with but spaced from the other of the pair of stator pole pieces by a predetermined air gap. The transducer further includes an energising winding for connection to an a.c. source and magnetically coupled with the rotor, and an output winding surrounding one of the pair of stator pole pieces, whereby on energisation of the energising winding, angular movement of the rotor varies the relative flux densities in the pair of stator pole pieces, and hence the voltage induced in the output winding will be dependent upon the angular position of the rotor.

United States Patent [1 1 Williams et al.

[11] 3,781,580 Dec. 25, 1973 [54] INDUCTOR ALTERNATOR [73] Assignee:Joseph Lucas (Industries) Limited,

Birmingham, England 221 Filed: July 28,1972 211 Appl. No.: 276,160

[30] Foreign Application Priority Data Primary Examiner-D. F. DugganAtt0rneyJohn C. Holman et al.

[57] ABSTRACT A transducer includes a stator formed of a magnetisablematerial and arranged to define at least one pair of adjacent polepieces, and a rotor formed of a magnetisable material and arranged todefine at least one pole piece. The rotor is movable angularly withrespect to the stator from a first position, in which the one rotor polepiece is aligned with but spaced from one of the pair of stator polepieces by a predetermined air gap, to a second position, in which theone rotor pole piece is aligned with but spaced from the other of thepair of stator pole pieces by a predetermined air gap. The transducerfurther includes an energising winding for connection to an ac. sourceand magnetically coupled with the rotor, and an output windingsurrounding one of the pair of stator pole pieces, whereby onenergisation of the energising winding, angular movement of the rotorvaries the relative flux densities in the pair of stator pole pieces,and hence the voltage induced in the output winding will be dependentupon the angular position of the rotor.

12 Claims, 4 Drawing Figures 1 INDUCTERALTERNATOR This invention relatesto transducers.

A transducer, accordingto the invention, includes a stator formed of amagnetisable material and arranged to define at least one pair ofadjacent pole pieces, a rotor formed of a magnetisable material andarranged to define at least one polepiece, said rotor being movableangularly with respect to said stator from a first position, in whichsaid one rotor pole piece is aligned with but spaced from oneof saidpair of stator pole pieces by a predetermined air gap, to a secondposition, in which said one rotor pole piece is aligned with but spacedfrom the other of said pair of stator pole pieces by a predetermined airgap, an energising winding for connection to an, a.c. source andmagnetically coupled with said rotor, and an output winding surroundingone of said pair of stator pole pieces, whereby on energisationof saidenergising winding, angular movement of said rotor varies the relativeflux densities in said pair of stator polepieces, and-hence the voltageinduced in said output winding will be dependentupon the angularposition of said rotor.

Preferably said statoris in the form of a cup-shaped member havingtherein .a central core, the wall of the cup-shaped member defining saidpair of adjacent pole pieces together with a further pair of adjacentpole pieces, a further output winding surrounding one of said furtherpair of adjacent pole pieces, and the rotor extending between thecentral core and the wall of the cup-shaped member and carrying afurther pole-piece, whereby angular movement of the rotor, in use,varies the relative flux densities in said further adjacent pole pieces,so that the-voltage induced in the further output winding, in use, isdependent upon the angular position of the rotor.

Preferably, the first mentioned output winding and said further outputwinding are connected in series with one another so that the voltagesinduced in the output windings, in use, are summed.

In the accompanying drawings,

FIG. 1 is a sectional view of a transducer according. to a first exampleof the invention,

FIG. 2 is a plan view of FIG. 1,

FIG. 3 is a sectional view of a transducer according to a second exampleof the invention, and

FIG. 4 is a graph illustrating the relationship between i the outputvoltage and the angular position of the rotor for a transducer accordingto the invention.

Referring to FIGS. 1 and 2, in a first example of the invention, thetransducer includes a stator 11 formed of a manganese/zinc ferrite assold by Mullard Ltd., as type AS. The stator 11 is in the form of asubstantially cup-shaped body 12 from the base 13 of which extends anintegral, hollow, cylindrical core 14. The axis of the core 14 isarranged to be parallel with and centrally disposed with respect to thecircular wall 15 of the cupshaped body 12 and the free ends of the core14 and the wall 15 respectively are arranged to lie in a plane parallelwith the base 13. The wall 15 of the body 12 is arranged to define fourequi-angularly spaced pole pieces 16 and a groove 17 extending parallelwith the axis of the core 14 is formed in the wall 15 intermediate eachpair of adjacent pole pieces 16. The grooves 17 serve to accommodateoutput windings 18 which surround one diametrically opposite pair of thepole pieces 16. The core 14 of thestator 11 also defines a pole piece ofthe stator 11 and an energising winding 19 surrounds the core 14.

Positioned within the bore in the hollow core 14 is a p.t.f.e. bearingsleeve 21 and extending through the sleeve 21 for movement relative tothe stator 11 is a non-magnetic and preferably brass drive shaft 22. Thedrive shaft 22 extends from the free end of the core 14 and isnon-rotatably secured to a rotor 23 formed of the same manganese/zincferrite as the stator l 1. The winding 19 is magnetically coupled withthe rotor 23 and the rotor which has a pair of opposed planar surfacesincludes a central rectangular portion 23a provided at each of a pair ofopposite edges with an arcuate portion 23b defining a pole piece of therotor. The portions 23b are each arranged to define part of a sector ofa circle centred on the axis of the core 14 but of radius greater thanthe radius of the wall 15 so that the rotor 23 extends between the core14 and the wall 15. Moreover, the arcuate length of each arcuate portion23b is greater than the arcuate length of each pole piece of the statorso that when said arcuate portion is axially aligned with one of saidstator pole pieces said arcuate portion extends partly over gaps definedbetween said one stator pole piece and a pair of adjacent stator polepieces. Positioned between the rotor 23 and the core 14 is a p.t.f.e.washer 24 which serves to permit angular movement of the rotor relativeto the stator 11 and also provides an air gap between each rotor polepiece and the wall 15 of the stator 11.

In use, the energising winding 19 is connected to an ac. source and theshaft 22 is coupled to an angularly movable member (not shown), theangular position of which is to be measured. Thus, angular movement ofsaid member is transmitted by the shaft 22 to the rotor 23 so as to movethe rotor angularly relative to the pole pieces 16. By virtue of the ac.signal supplied to the winding 19, there is a magnetic flux linkagebetween the rotor pole pieces 23b and the pole pieces 16 so thatvariation in the angular position of the rotor with respect to the polepieces 16 varies the flux densities in the pole pieces 16 respectively.Thus the voltage induced in the output windings 18 will be dependentupon the angular position of the rotor 23 and hence on the angularposition of said angularly movable member. Preferably, the outputwindings 18 are connected together in series in such a manner that theoutputs from the windings, in use, are summed. In this way, it ispossible to overcome the effect of any variation in the air gap betweenthe wall 15 and the rotor pole pieces 23b due to tilt of the rotor asthe rotor is moved angularly in use.

Referring now to FIG. 3, there is shown a transducer which correspondsclosely to that described above and accordingly, the same referencenumerals are used in FIG. 3 to indicate corresponding parts of thetransducer described with reference to FIGS. 1 and 2. However, by way ofcontrast to the transducer according to the first example, thetransducershown in FIG. 3 is provided with 'an energising winding 31 which,instead of surrounding the core'14 of the stator 11, is mounted abovethe core 14 on an extension thereof and surrounds the centrally disposedlimb 32 of an inverted E shaped rotor 33, the free edges of the threelimbs of the rotor being disposed adjacent to the stator 11. The winding31 is, however, magnetically coupled with the E shaped rotor 33 and theouter limbs 34 of the E shaped rotor define respective pole pieces ofthe rotor so that operation of the transducer is th e same as thatdescribed above. 7

It is to be appreciated that the transducer according to the inventionprovides an output which varies substantially linearly with the angularposition of the rotor over a wide range of angular positions of therotor. The highly desirable performance of the transducer according tothe invention is illustrated in FIG. 4, which is a graph of outputvoltage drawn against angular position of the rotor for a square waveinput to the energising winding.

It will be appreciated that, although in the examples given the air gapbetween each pole piece of the rotor and the wall of the stator 11 ismaintained by a washer, appropriate bearings between rotor and statorcan be used to provide the air gap, and the'washer eliminated. g

It will be appreciated that the rotor may be attached to the shaft bymeans other than that described, for example, the magnetising materialcould besecured, such as by use of an'adhesive, to a non-magneticframework.

We claim:

1. A transducer including a stator which is formed of magnetisablematerial and which is in the form of a cup-shaped member having thereina central core the wall of the cup-shaped member defining two pairs ofadjacent pole pieces, a rotor formed of magnetisable material andextending between the central core and the wall of the cup-shaped memberand defining two pole pieces, the rotor being movable angularly withrespect to said stator from a first position, in which the rotor polepieces are aligned with, but spaced from one of each of said pairs ofstator pole pieces respectively by a predetermined air gap, toasecondposition, in which said rotor pole pieces are aligned with, but

varies the relative flux densities in said pair of stator pole pieces,and hence the voltage induced in said out-' put winding will bedependent uponthe angular position of said rotor.

2. A transducer as claimed in claim 1 wherein the surface of the rotorfacing the pole pieces of the stator is planar. I

3. A transducer as claimed in claim 1 wherein the two output windingsare connected in series with one another so that the voltages induced inthe output windings, in use, are summed.

4. A transducer as claimed in claim 1 wherein said rotor includes acentral rectangular portion provided at each of a pair of opposite sideswith an arcuate portion defining a pole piece of the rotor.

. 5. A transducer as claimed in claim 4 wherein the arcuatelength ofeach arcuate portion is greater than the arcuate length of each polepiece ofthe stator so that when said arcuate portion is axially alignedwith one of said stator pole pieces said arcuate portion extendspartlyover gaps defined between said one stator pole piece and a pair ofadjacent stator pole pieces.

6. A transducer as claimed in claim 1 wherein the rotor is E-shaped andwherein the two outer limbs of the rotor define pole pieces of therotor.

7. A transducer as claimed in claim 6 wherein the free edges of thethree limbs of the rotor are disposed adjacent to the stator.

spaced from the other pole piece of each of. said pair 8. A transduceras claimed in claim 7 wherein said energi'sing winding is wound aboutthe central limb of the E-shaped rotor.

9. A transducer as claimed in claim 8 wherein the energising winding iswound on an extension of the stator core so as to surround the centrallimb of the rotor.

10. A transducer asclaimed in claim 1 wherein said rotor is mounged forrotation about the axis of said central core.

. 11; A transducer as claimed in claim 10 wherein said central core ishollow, said rotor being mounted on a shaft rotatable with said hollowcore.

12. A transducer as claimed in claim 11 wherein said I shaft is formedof non-magnetic material.

1. A transducer including a stator which is formed of magnetisablematerial and which is in the form of a cup-shaped member having thereina central core the wall of the cup-shaped member defining two pairs ofadjacent pole pieces, a rotor formed of magnetisable material andextending between the central core and the wall of the cup-shaped memberand defining two pole pieces, the rotor being movable angularly withrespect to said stator from a first position, in which the rotor polepieces are aligned with, but spaced from one of each of said pairs ofstator pole pieces respectively by a predetermined air gap, to a secondposition, in which said rotor pole pieces are aligned with, but spacedfrom the other pole piece of each of said pair of stator pole piecesrespectively by a predetermined air gap, a single energising winding forconnection to an a.c. source and magnetically coupled with said rotor,and a pair of output windings surrounding only one diametricallyopposite pair of pole pieces which are equi-angularly spaced, wherebyupon energisation of said energising winding, angular movement of saidrotor varies the relative flux densities in said pair of stator polepieces, and hence the voltage induced in said output winding will bedependent upon the angular position of said rotor.
 2. A transducer asclaimed in claim 1 wherein the surface of the rotor facing the polepieces of the stator is planar.
 3. A transducer as claimed in claim 1wherein the two output windings are connected in series with one anotherso that the voltages induced in the output windings, in use, are summed.4. A transducer as claimed in claim 1 wherein said rotor includes acentral rectangular portion provided at each of a pair of opposite sideswith an arcuate portion defining a pole piece of the rotor.
 5. Atransducer as claimed in claim 4 wherein the arcuate length of eacharcuate portion is greater than the arcuate length of each pole piece ofthe stator so that when said arcuate portion is axially aligned with oneof said stator pole pieces said arcuate portion extends partly over gapsdefined between said one stator pole piece and a pair of adjacent statorpole pieces.
 6. A transducer as claimeD in claim 1 wherein the rotor isE-shaped and wherein the two outer limbs of the rotor define pole piecesof the rotor.
 7. A transducer as claimed in claim 6 wherein the freeedges of the three limbs of the rotor are disposed adjacent to thestator.
 8. A transducer as claimed in claim 7 wherein said energisingwinding is wound about the central limb of the E-shaped rotor.
 9. Atransducer as claimed in claim 8 wherein the energising winding is woundon an extension of the stator core so as to surround the central limb ofthe rotor.
 10. A transducer as claimed in claim 1 wherein said rotor ismounged for rotation about the axis of said central core.
 11. Atransducer as claimed in claim 10 wherein said central core is hollow,said rotor being mounted on a shaft rotatable with said hollow core. 12.A transducer as claimed in claim 11 wherein said shaft is formed ofnon-magnetic material.